To submit a sitemap to Google, you need to use Google Search Console. Here's how:
Make sure your sitemap is in XML format and it adheres to the sitemap protocol.
Sign in to Google Search Console (or create an account if you don't have one).
Add your website as a new property in Google Search Console.
Once your website is verified, click on 'Sitemaps' from the left hand menu.
In the 'Add a new sitemap' section, enter the URL of your sitemap and click 'Submit'.
Google will then start crawling the URLs listed in your sitemap. It could take several days for all URLs to be crawled.
Here's a sample of what your sitemap XML file might look like:
In the XML above,
<loc> specifies the URL of the page.
<lastmod> is when the page was last modified,
<changefreq> is how frequently the page changes, and
<priority> is the priority of this URL relative to other URLs on your site.